where \(F(\delta )\)  is the complementary cumulative distribution function that measures the probability that a randomly placed sphere of radius \(\delta \)  centered in the pore space \(\mathcal {V}_1\)  lies entirely in \(\mathcal {V}_1\) . We have that \(F(0)=1\)  and \(F(\infty )=0\) , and it immediately follows that \(P(0)=s/\phi _1\)  and \(P(\infty )=0\) . The \(n\) th moment of the pore-size probability density function is [1]}
\(\langle \delta ^n \rangle \equiv \int _0^{\infty } \delta ^n P(\delta ) d\delta .\) 
